Islamic State militants have returned in explosive numbers to using a heavily encrypted phone messaging and social networking application whose Russian developer came under widespread political and law-enforcement pressure after November's Paris attacks to hinder jihadi use of his hard-to-crack technology.

Telegram's Pavel Durov consistently refused to block IS and other jihadi groups from using his platform before the Paris attacks but reluctantly blocked 78 IS-related accounts on his Berlin-based secure messaging app after terrorists killed 130 people in the French capital.

Telegram’s Channels Service, which was launched last September, allows messages to be transmitted to an unlimited number of subscribers and for users to break off into highly encrypted private and group chats. In the last few weeks IS militants and other jihadis have resorted again — but in even larger numbers — to the Telegram app to recruit, spread propaganda and, intelligence officials fear, possibly organize and plot attacks in chats that are invisible and can’t be monitored or decoded.

According to Steve Stalinsky, executive director of a jihadist monitoring research group based in Washington, Telegram has the potential to surpass Twitter as the messaging tool of choice for Islamic State and al-Qaida groups.

“The Taliban has created, for the first time, accounts on Telegram just in the past couple of days,” he says.

American and European officials say they have no final evidence that the Paris attackers used difficult-to-crack encryption technologies to plot their violence but, with the chief planners back in Syria, some form of secure communications would have been needed, they say.

Much of the national security leadership of the Obama administration is to discuss Friday with Silicon Valley chiefs jihadi use of the Internet to recruit and radicalize people and plot attacks.

FILE - Pavel Durov.

App founder

The traffic and use of Telegram, which is based in Germany, is “shocking,” says Stalinsky, who runs the Middle East Media Research Institute (MEMRI). The app was developed by the brothers Pavel and Nikolai Durov. Pavel Durov, 31, is best known for having founded the social networking site VK, a Russian version of Facebook that earned him the nickname the “Mark Zuckerberg of Russia.” He holds strong libertarian political views and he says he lost control of VK to allies of Russian President Vladimir Putin after he refused to comply with Kremlin orders to provide personal details of VK users, including Maidan protesters in Ukraine, to Russian security agencies.

Says Stalinsky: “We have been focused on jihadi use of Telegram since October and before the Paris attacks we saw unprecedented growth for an app — it was the biggest development in cyber-jihad since the jihadis started to communicate on Twitter two years ago. Durov came under pressure and grudgingly closed accounts, but they are all back now and there are many more of them. And every day there are even more. It is crazy — on one channel alone overnight last night there were more than 10,000 chats.”

Telegram is more sophisticated than Twitter, having among other features state-of-the-art built-in encryption technology that Durov’s company boasts is more secure than mass market messengers like WhatsApp.

Anonymity

On the Telegram channels, which are designed to allow public messages to be sent to large audiences, there is relative anonymity. A channel displays only the total number of its subscribers to other users without disclosing real names. Following and follower lists are public on Twitter, allowing pro-IS accounts to be cross-referenced by checking the accounts they follow and those that follow them.

Telegram users can forward content from a channel to other Telegram users allowing the dissemination of jihadi content. Content on IS-linked channels include tutorials on making weapons and calls for lone-wolf attacks.

Messages on the channels are transmitted in a single direction and subscribers can’t send content to a sender. This blocks the possibility — in contrast to Twitter — of counter-messaging — a strategy used by Western governments to push back against extremist propaganda.

As well as the channels, subscribers can break off into private and group chats of up to 1,000 members. Telegram also offers Secret Chats, which use end-to-end encryption, leave no trace on the Telegram servers and support self-destructing messages,” the company brags.

FILE - Former U.S. National Security Agency contractor Edward Snowden.

Aiding and abetting

U.S. and European officials have long complained that high-tech companies are in effect aiding and abetting terrorism.

Last year, British spy chief Robert Hannigan complained they had become “the command-and-control networks of choice for terrorists and criminals — precisely because they are highly encrypted.”

After initial resistance to government complaints, Facebook, Google and Twitter have been readier to co-operate with authorities to remove extremist messages on their sites but have resisted providing a so-called backdoor for governments with encryption keys. Apple has developed keys that the users at each end of the conversation hold and are not possessed by the company itself and its chief executive, Timothy Cook, has argued: “If you put a key under the mat for the cops, a burglar can find it, too.”

Silicon Valley chiefs say they fear violations of privacy and that their priority is their customers — not national security, an argument that has resonated since disclosures, by Edward Snowden, a former contractor with the U.S. National Security Agency, revealed the extent of electronic surveillance by U.S. intelligence agencies.

In the meantime, though, IS and other jihadis remain less hindered as they communicate, recruit and plot. On Telegram, there are several channels now run by IS media groups Nashir, Fursan Al-Raf, and Al-Battar. A group titled the “Supporters of the Islamic State”, whose avatar is of IS leader Abu Bakr al-Baghdadi, was established on December 17 and within two days had 500 subscribers.